Android IPC 通信方式介绍
01.使用Intent
- 1.Activity,Service,Receiver 都支持在 Intent 中传递 Bundle 数据,而 Bundle 实现了 Parcelable 接口,可以在不同的进程间进行传输。
- 2.在一个进程中启动了另一个进程的 Activity,Service 和 Receiver ,可以在 Bundle 中附加要传递的数据通过 Intent 发送出去。
02.使用文件共享
- 1.Windows 上,一个文件如果被加了排斥锁会导致其他线程无法对其进行访问,包括读和写;而 Android 系统基于 Linux ,使得其并发读取文件没有限制地进行,甚至允许两个线程同时对一个文件进行读写操作,尽管这样可能会出问题。
- 2.可以在一个进程中序列化一个对象到文件系统中,在另一个进程中反序列化恢复这个对象(注意:并不是同一个对象,只是内容相同。)。
- 3.SharedPreferences 是个特例,系统对它的读 / 写有一定的缓存策略,即内存中会有一份 ShardPreferences 文件的缓存,系统对他的读 / 写就变得不可靠,当面对高并发的读写访问,SharedPreferences 有很多大的几率丢失数据。因此,IPC 不建议采用 SharedPreferences。
03.使用Messenger
Messenger 是一种轻量级的 IPC 方案,它的底层实现是 AIDL ,可以在不同进程中传递 Message 对象,它一次只处理一个请求,在服务端不需要考虑线程同步的问题,服务端不存在并发执行的情形。
服务端进程:
- 服务端创建一个 Service 来处理客户端请求,同时通过一个 Handler 对象来实例化一个 Messenger 对象,然后在 Service 的 onBind 中返回这个 Messenger 对象底层的 Binder 即可。
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42public class MessengerService extends Service {
private static final String TAG = MessengerService.class.getSimpleName();
private class MessengerHandler extends Handler {
/**
* @param msg
*/
public void handleMessage(Message msg) {
switch (msg.what) {
case Constants.MSG_FROM_CLIENT:
Log.d(TAG, "receive msg from client: msg = [" + msg.getData().getString(Constants.MSG_KEY) + "]");
Toast.makeText(MessengerService.this, "receive msg from client: msg = [" + msg.getData().getString(Constants.MSG_KEY) + "]", Toast.LENGTH_SHORT).show();
Messenger client = msg.replyTo;
Message replyMsg = Message.obtain(null, Constants.MSG_FROM_SERVICE);
Bundle bundle = new Bundle();
bundle.putString(Constants.MSG_KEY, "我已经收到你的消息,稍后回复你!");
replyMsg.setData(bundle);
try {
client.send(replyMsg);
} catch (RemoteException e) {
e.printStackTrace();
}
break;
default:
super.handleMessage(msg);
}
}
}
private Messenger mMessenger = new Messenger(new MessengerHandler());
public IBinder onBind(Intent intent) {
return mMessenger.getBinder();
}
}客户端进程:
- 首先绑定服务端 Service ,绑定成功之后用服务端的 IBinder 对象创建一个 Messenger ,通过这个 Messenger 就可以向服务端发送消息了,消息类型是 Message 。如果需要服务端响应,则需要创建一个 Handler 并通过它来创建一个 Messenger(和服务端一样),并通过 Message 的 replyTo 参数传递给服务端。服务端通过 Message 的 replyTo 参数就可以回应客户端了。
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85public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName();
private Messenger mGetReplyMessenger = new Messenger(new MessageHandler());
private Messenger mService;
private class MessageHandler extends Handler {
public void handleMessage(Message msg) {
switch (msg.what) {
case Constants.MSG_FROM_SERVICE:
Log.d(TAG, "received msg form service: msg = [" + msg.getData().getString(Constants.MSG_KEY) + "]");
Toast.makeText(MainActivity.this, "received msg form service: msg = [" + msg.getData().getString(Constants.MSG_KEY) + "]", Toast.LENGTH_SHORT).show();
break;
default:
super.handleMessage(msg);
}
}
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void bindService(View v) {
Intent mIntent = new Intent(this, MessengerService.class);
bindService(mIntent, mServiceConnection, Context.BIND_AUTO_CREATE);
}
public void sendMessage(View v) {
Message msg = Message.obtain(null,Constants.MSG_FROM_CLIENT);
Bundle data = new Bundle();
data.putString(Constants.MSG_KEY, "Hello! This is client.");
msg.setData(data);
msg.replyTo = mGetReplyMessenger;
try {
mService.send(msg);
} catch (RemoteException e) {
e.printStackTrace();
}
}
protected void onDestroy() {
unbindService(mServiceConnection);
super.onDestroy();
}
private ServiceConnection mServiceConnection = new ServiceConnection() {
/**
* @param name
* @param service
*/
public void onServiceConnected(ComponentName name, IBinder service) {
mService = new Messenger(service);
Message msg = Message.obtain(null,Constants.MSG_FROM_CLIENT);
Bundle data = new Bundle();
data.putString(Constants.MSG_KEY, "Hello! This is client.");
msg.setData(data);
//
msg.replyTo = mGetReplyMessenger;
try {
mService.send(msg);
} catch (RemoteException e) {
e.printStackTrace();
}
}
/**
* @param name
*/
public void onServiceDisconnected(ComponentName name) {
}
};
}注意:客户端和服务端是通过拿到对方的 Messenger 来发送 Message 的。
- 客户端通过 bindService onServiceConnected 而服务端通过 message.replyTo 来获得对方的 Messenger 。Messenger中有一个Hanlder以串行的方式处理队列中的消息。不存在并发执行,因此我们不用考虑线程同步的问题。
04.使用AIDL
- Messenger 是以串行的方式处理客户端发来的消息,如果大量消息同时发送到服务端,服务端只能一个一个处理,所以大量并发请求就不适合用Messenger,而且Messenger只适合传递消息,不能跨进程调用服务端的方法。
- AIDL 可以解决并发和跨进程调用方法的问题,要知道Messenger本质上也是AIDL,只不过系统做了封装方便上层的调用而已。
4.1 AIDL文件支持的数据类型
- 基本数据类型;
- String 和 CharSequence
- ArrayList ,里面的元素必须能够被 AIDL 支持;
- HashMap ,里面的元素必须能够被 AIDL 支持;
- Parcelable ,实现 Parcelable 接口的对象;
注意:如果 AIDL 文件中用到了自定义的 Parcelable 对象,必须新建一个和它同名的 AIDL 文件。 - AIDL ,AIDL 接口本身也可以在 AIDL 文件中使用。
4.2 服务端
- 服务端创建一个 Service 用来监听客户端的连接请求,然后创建一个 AIDL 文件,将暴露给客户端的接口在这个 AIDL 文件中声明,最后在 Service 中实现这个 AIDL 接口即可。
4.3客户端
- 绑定服务端的 Service ,绑定成功后,将服务端返回的 Binder 对象转成 AIDL 接口所属的类型,然后就可以调用 AIDL 中的方法了。客户端调用远程服务的方法,被调用的方法运行在服务端的 Binder 线程池中,同时客户端的线程会被挂起,如果服务端方法执行比较耗时,就会导致客户端线程长时间阻塞,导致 ANR 。客户端的 onServiceConnected 和 onServiceDisconnected 方法都在 UI 线程中。
05.使用ContentProvider
用于不同应用间数据共享,和 Messenger 底层实现同样是 Binder 和 AIDL,系统做了封装,使用简单。
系统预置了许多 ContentProvider ,如通讯录、日程表,需要跨进程访问。使用方法:继承 ContentProvider 类实现 6 个抽象方法,这六个方法均运行在 ContentProvider 进程中,除 onCreate 运行在主线程里,其他五个方法均由外界回调运行在 Binder 线程池中。ContentProvider 的底层数据,可以是 SQLite 数据库,可以是文件,也可以是内存中的数据。
详见代码:
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119public class BookProvider extends ContentProvider {
private static final String TAG = "BookProvider";
public static final String AUTHORITY = "com.jc.ipc.Book.Provider";
public static final Uri BOOK_CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/book");
public static final Uri USER_CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/user");
public static final int BOOK_URI_CODE = 0;
public static final int USER_URI_CODE = 1;
private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
static {
sUriMatcher.addURI(AUTHORITY, "book", BOOK_URI_CODE);
sUriMatcher.addURI(AUTHORITY, "user", USER_URI_CODE);
}
private Context mContext;
private SQLiteDatabase mDB;
@Override
public boolean onCreate() {
mContext = getContext();
initProviderData();
return true;
}
private void initProviderData() {
//不建议在 UI 线程中执行耗时操作
mDB = new DBOpenHelper(mContext).getWritableDatabase();
mDB.execSQL("delete from " + DBOpenHelper.BOOK_TABLE_NAME);
mDB.execSQL("delete from " + DBOpenHelper.USER_TABLE_NAME);
mDB.execSQL("insert into book values(3,'Android');");
mDB.execSQL("insert into book values(4,'iOS');");
mDB.execSQL("insert into book values(5,'Html5');");
mDB.execSQL("insert into user values(1,'haohao',1);");
mDB.execSQL("insert into user values(2,'nannan',0);");
}
@Nullable
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
Log.d(TAG, "query, current thread"+ Thread.currentThread());
String table = getTableName(uri);
if (table == null) {
throw new IllegalArgumentException("Unsupported URI" + uri);
}
return mDB.query(table, projection, selection, selectionArgs, null, null, sortOrder, null);
}
@Nullable
@Override
public String getType(Uri uri) {
Log.d(TAG, "getType");
return null;
}
@Nullable
@Override
public Uri insert(Uri uri, ContentValues values) {
Log.d(TAG, "insert");
String table = getTableName(uri);
if (table == null) {
throw new IllegalArgumentException("Unsupported URI" + uri);
}
mDB.insert(table, null, values);
// 通知外界 ContentProvider 中的数据发生变化
mContext.getContentResolver().notifyChange(uri, null);
return uri;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
Log.d(TAG, "delete");
String table = getTableName(uri);
if (table == null) {
throw new IllegalArgumentException("Unsupported URI" + uri);
}
int count = mDB.delete(table, selection, selectionArgs);
if (count > 0) {
mContext.getContentResolver().notifyChange(uri, null);
}
return count;
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
Log.d(TAG, "update");
String table = getTableName(uri);
if (table == null) {
throw new IllegalArgumentException("Unsupported URI" + uri);
}
int row = mDB.update(table, values, selection, selectionArgs);
if (row > 0) {
getContext().getContentResolver().notifyChange(uri, null);
}
return row;
}
private String getTableName(Uri uri) {
String tableName = null;
switch (sUriMatcher.match(uri)) {
case BOOK_URI_CODE:
tableName = DBOpenHelper.BOOK_TABLE_NAME;
break;
case USER_URI_CODE:
tableName = DBOpenHelper.USER_TABLE_NAME;
break;
default:
break;
}
return tableName;
}
}DBOpenHelper代码如下所示
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33public class DBOpenHelper extends SQLiteOpenHelper {
private static final String DB_NAME = "book_provider.db";
public static final String BOOK_TABLE_NAME = "book";
public static final String USER_TABLE_NAME = "user";
private static final int DB_VERSION = 1;
private String CREATE_BOOK_TABLE = "CREATE TABLE IF NOT EXISTS "
+ BOOK_TABLE_NAME + "(_id INTEGER PRIMARY KEY," + "name TEXT)";
private String CREATE_USER_TABLE = "CREATE TABLE IF NOT EXISTS "
+ USER_TABLE_NAME + "(_id INTEGER PRIMARY KEY," + "name TEXT,"
+ "sex INT)";
public DBOpenHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK_TABLE);
db.execSQL(CREATE_USER_TABLE);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}测试代码
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77public class ProviderActivity extends AppCompatActivity {
private static final String TAG = ProviderActivity.class.getSimpleName();
private TextView displayTextView;
private Handler mHandler;
protected void onCreate( { Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_provider);
displayTextView = (TextView) findViewById(R.id.displayTextView);
mHandler = new Handler();
getContentResolver().registerContentObserver(BookProvider.BOOK_CONTENT_URI, true, new ContentObserver(mHandler) {
public boolean deliverSelfNotifications() {
return super.deliverSelfNotifications();
}
public void onChange(boolean selfChange) {
super.onChange(selfChange);
}
public void onChange(boolean selfChange, Uri uri) {
Toast.makeText(ProviderActivity.this, uri.toString(), Toast.LENGTH_SHORT).show();
super.onChange(selfChange, uri);
}
});
}
public void insert(View v) {
ContentValues values = new ContentValues();
values.put("_id",1123);
values.put("name", "三国演义");
getContentResolver().insert(BookProvider.BOOK_CONTENT_URI, values);
}
public void delete(View v) {
getContentResolver().delete(BookProvider.BOOK_CONTENT_URI, "_id = 4", null);
}
public void update(View v) {
ContentValues values = new ContentValues();
values.put("_id",1123);
values.put("name", "三国演义新版");
getContentResolver().update(BookProvider.BOOK_CONTENT_URI, values , "_id = 1123", null);
}
public void query(View v) {
Cursor bookCursor = getContentResolver().query(BookProvider.BOOK_CONTENT_URI, new String[]{"_id", "name"}, null, null, null);
StringBuilder sb = new StringBuilder();
while (bookCursor.moveToNext()) {
Book book = new Book(bookCursor.getInt(0),bookCursor.getString(1));
sb.append(book.toString()).append("\n");
}
sb.append("--------------------------------").append("\n");
bookCursor.close();
Cursor userCursor = getContentResolver().query(BookProvider.USER_CONTENT_URI, new String[]{"_id", "name", "sex"}, null, null, null);
while (userCursor.moveToNext()) {
sb.append(userCursor.getInt(0))
.append(userCursor.getString(1)).append(" ,")
.append(userCursor.getInt(2)).append(" ,")
.append("\n");
}
sb.append("--------------------------------");
userCursor.close();
displayTextView.setText(sb.toString());
}
}
06.使用Socket
Socket起源于 Unix,而 Unix 基本哲学之一就是“一切皆文件”,都可以用“打开 open –读写 write/read –关闭 close ”模式来操作。Socket 就是该模式的一个实现,网络的 Socket 数据传输是一种特殊的 I/O,Socket 也是一种文件描述符。Socket 也具有一个类似于打开文件的函数调用: Socket(),该函数返回一个整型的Socket 描述符,随后的连接建立、数据传输等操作都是通过该 Socket 实现的。
常用的 Socket 类型有两种:流式 Socket(SOCK_STREAM)和数据报式 Socket(SOCK_DGRAM)。流式是一种面向连接的 Socket,针对于面向连接的 TCP 服务应用;数据报式 Socket 是一种无连接的 Socket ,对应于无连接的 UDP 服务应用。
- Socket 本身可以传输任意字节流。谈到Socket,就必须要说一说 TCP/IP 五层网络模型:
- 应用层:规定应用程序的数据格式,主要的协议 HTTP,FTP,WebSocket,POP3 等;
- 传输层:建立“端口到端口” 的通信,主要的协议:TCP,UDP;
- 网络层:建立”主机到主机”的通信,主要的协议:IP,ARP ,IP 协议的主要作用:一个是为每一台计算机分配 IP 地址,另一个是确定哪些地址在同一子网;
- 数据链路层:确定电信号的分组方式,主要的协议:以太网协议;
- 物理层:负责电信号的传输。
- Socket 是连接应用层与传输层之间接口(API)。
5.1Client 端代码:
代码如下所示
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121public class TCPClientActivity extends AppCompatActivity implements View.OnClickListener{
private static final String TAG = "TCPClientActivity";
public static final int MSG_RECEIVED = 0x10;
public static final int MSG_READY = 0x11;
private EditText editText;
private TextView textView;
private PrintWriter mPrintWriter;
private Socket mClientSocket;
private Button sendBtn;
private StringBuilder stringBuilder;
private Handler mHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_READY:
sendBtn.setEnabled(true);
break;
case MSG_RECEIVED:
stringBuilder.append(msg.obj).append("\n");
textView.setText(stringBuilder.toString());
break;
default:
super.handleMessage(msg);
}
}
};
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tcp_client_activity);
editText = (EditText) findViewById(R.id.editText);
textView = (TextView) findViewById(R.id.displayTextView);
sendBtn = (Button) findViewById(R.id.sendBtn);
sendBtn.setOnClickListener(this);
sendBtn.setEnabled(false);
stringBuilder = new StringBuilder();
Intent intent = new Intent(TCPClientActivity.this, TCPServerService.class);
startService(intent);
new Thread(){
@Override
public void run() {
connectTcpServer();
}
}.start();
}
private String formatDateTime(long time) {
return new SimpleDateFormat("(HH:mm:ss)").format(new Date(time));
}
private void connectTcpServer() {
Socket socket = null;
while (socket == null) {
try {
socket = new Socket("localhost", 8888);
mClientSocket = socket;
mPrintWriter = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())
), true);
mHandler.sendEmptyMessage(MSG_READY);
} catch (IOException e) {
e.printStackTrace();
}
}
// receive message
BufferedReader bufferedReader = null;
try {
bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
} catch (IOException e) {
e.printStackTrace();
}
while (!isFinishing()) {
try {
String msg = bufferedReader.readLine();
if (msg != null) {
String time = formatDateTime(System.currentTimeMillis());
String showedMsg = "server " + time + ":" + msg
+ "\n";
mHandler.obtainMessage(MSG_RECEIVED, showedMsg).sendToTarget();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
@Override
public void onClick(View v) {
if (mPrintWriter != null) {
String msg = editText.getText().toString();
mPrintWriter.println(msg);
editText.setText("");
String time = formatDateTime(System.currentTimeMillis());
String showedMsg = "self " + time + ":" + msg + "\n";
stringBuilder.append(showedMsg);
}
}
@Override
protected void onDestroy() {
if (mClientSocket != null) {
try {
mClientSocket.shutdownInput();
mClientSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
super.onDestroy();
}
}
5.2 Server 端代码
代码如下所示
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95public class TCPServerService extends Service {
private static final String TAG = "TCPServerService";
private boolean isServiceDestroyed = false;
private String[] mMessages = new String[]{
"Hello! Body!",
"用户不在线!请稍后再联系!",
"请问你叫什么名字呀?",
"厉害了,我的哥!",
"Google 不需要科学上网是真的吗?",
"扎心了,老铁!!!"
};
public void onCreate() {
new Thread(new TCPServer()).start();
super.onCreate();
}
public void onDestroy() {
isServiceDestroyed = true;
super.onDestroy();
}
public IBinder onBind(Intent intent) {
return null;
}
private class TCPServer implements Runnable {
public void run() {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(8888);
} catch (IOException e) {
e.printStackTrace();
return;
}
while (!isServiceDestroyed) {
// receive request from client
try {
final Socket client = serverSocket.accept();
Log.d(TAG, "=============== accept ==================");
new Thread(){
public void run() {
try {
responseClient(client);
} catch (IOException e) {
e.printStackTrace();
}
}
}.start();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
private void responseClient(Socket client) throws IOException {
//receive message
BufferedReader in = new BufferedReader(
new InputStreamReader(client.getInputStream()));
//send message
PrintWriter out = new PrintWriter(
new BufferedWriter(
new OutputStreamWriter(
client.getOutputStream())),true);
out.println("欢迎来到聊天室!");
while (!isServiceDestroyed) {
String str = in.readLine();
Log.d(TAG, "message from client: " + str);
if (str == null) {
return;
}
Random random = new Random();
int index = random.nextInt(mMessages.length);
String msg = mMessages[index];
out.println(msg);
Log.d(TAG, "send Message: " + msg);
}
out.close();
in.close();
client.close();
}
}